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20 Dec 2004

Volume 85, Issue 25, pp. 6083-6293

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 6281 (2004); http://dx.doi.org/10.1063/1.1834720 (3 pages)

M. P. Rao, M. F. Aimi, and N. C. MacDonald
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Superconducting properties of MgB2 films electroplated to stainless steel substrates

Hideki Abe, Kenji Nishida, Motoharu Imai, Hideaki Kitazawa, and Kenji Yoshii

Appl. Phys. Lett. 85, 6197 (2004); http://dx.doi.org/10.1063/1.1839644 (3 pages) | Cited 11 times

Online Publication Date: 15 December 2004

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Superconducting MgB2 films have been fabricated on stainless steel substrates by means of electroplating in a molten electrolyte composed of MgCl2, MgB2O4, NaCl, and KCl containing a fractional amount of CuCl2. Microscopic observation has revealed that the electroplated films and substrates are combined with each other through Cu-rich layers at the interfaces. Transport measurements have shown that the electroplated MgB2 films possess an upper critical field, Hc2(0), of 28 T, an irreversibility field, Hirr(0), of 13 T, and a critical current density, Jc(5 K,0 T), of 25 000 A∕cm2, which suggests that the electroplating in molten salts is a promising alternative to the powder-in-tube method for the fabrication of MgB2 tapes.
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74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.78.Na Mesoscopic and nanoscale systems
74.25.F- Transport properties
81.15.Pq Electrodeposition, electroplating
74.25.Sv Critical currents
74.25.Op Mixed states, critical fields, and surface sheaths
68.55.-a Thin film structure and morphology

The origin of signal-to-noise ratio improvements in laminated recording media

D. T. Margulies, M. E. Schabes, N. Supper, H. Do, A. Berger, A. Moser, P. M. Rice, P. Arnett, M. Madison, B. Lengsfield, H. Rosen, and Eric E. Fullerton

Appl. Phys. Lett. 85, 6200 (2004); http://dx.doi.org/10.1063/1.1831571 (3 pages) | Cited 3 times

Online Publication Date: 15 December 2004

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We report an experimental and theoretical study of laminated recording media made of two CoPtCrB magnetic layers separated by a Ru spacer layer. We find that a 4 math Ru spacer layer is sufficient to decorrelate the noise of the magnetic transitions in the two layers, thus producing improved media signal-to-noise ratios. This result is surprising given that the layers remain structurally correlated due to their epitaxial growth, and therefore the noise in the layers would be expected to be correlated as well. Experiments suggest that the reduced transition noise is produced by a slight shift between the transition locations in the layers. This shift is on the order of the grain size and allows the transitions to sample a different microstructure causing the noise associated with the transitions to be uncorrelated.
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75.50.Ss Magnetic recording materials
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Vv High coercivity materials

Giant Zeeman effect of excitons in a hybrid nanostructure of diluted magnetic semiconductor quantum well sandwiched in Co wires

M. Sakuma, K. Hyomi, I. Souma, A. Murayama, and Y. Oka

Appl. Phys. Lett. 85, 6203 (2004); http://dx.doi.org/10.1063/1.1841480 (3 pages) | Cited 6 times

Online Publication Date: 15 December 2004

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Giant Zeeman effects of excitons in a hybrid nanostructure of diluted magnetic semiconductor (DMS) quantum well (QW) with ferromagnetic Co have been demonstrated, where the DMS-QW wire with the width of 200 nm is sandwiched in the Co wires and magnetic fields nearly perpendicular to the well plane can efficiently be applied from the Co wires to all of the DMS QW. The spectral shape of excitonic photoluminescence and the field dependence show clearly that the microscopic perpendicular fields generated from the Co wires induce the giant Zeeman shifts of excitons in the DMS QW.
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75.50.Pp Magnetic semiconductors
75.50.Cc Other ferromagnetic metals and alloys
78.20.Ls Magneto-optical effects
78.67.De Quantum wells
73.21.Fg Quantum wells
73.22.Lp Collective excitations
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.Et II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Focused-ion-beam-induced deposition of superconducting nanowires

E. S. Sadki, S. Ooi, and K. Hirata

Appl. Phys. Lett. 85, 6206 (2004); http://dx.doi.org/10.1063/1.1842367 (3 pages) | Cited 34 times

Online Publication Date: 15 December 2004

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Superconducting nanowires, with a critical temperature of 5.2 K, have been synthesized using an ion-beam-induced deposition, with a gallium focused ion beam and tungsten carboxyl, W(CO)6, as precursor. The films are amorphous, with atomic concentrations of about 40%, 40%, and 20% for W, C, and Ga, respectively, 0 K values of the upper critical field and coherence length of 9.5 T and 5.9 nm, respectively, are deduced from the resistivity data at different applied magnetic fields. The critical current density is Jc=1.5×105 A∕cm2 at 3 K. This technique can be used as a template-free fabrication method for superconducting devices.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Jj Ion and electron beam-assisted deposition; ion plating
74.25.Sv Critical currents
74.25.Op Mixed states, critical fields, and surface sheaths
74.78.-w Superconducting films and low-dimensional structures
74.25.Ha Magnetic properties including vortex structures and related phenomena
61.46.-w Structure of nanoscale materials
84.71.Mn Superconducting wires, fibers, and tapes

Charge and spin distribution in ferromagnetic Mn-doped InGaAs∕GaAs multilayers

G. M. Sipahi, S. C. P. Rodrigues, L. M. R. Scolfaro, and I. C. da Cunha Lima

Appl. Phys. Lett. 85, 6209 (2004); http://dx.doi.org/10.1063/1.1840121 (3 pages) | Cited 3 times

Online Publication Date: 15 December 2004

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The search for materials tailored for spintronic devices led recently to the study of III–V diluted magnetic semiconductors (DMS). These materials are found to be closer to room-temperature ferromagnetism than their II–VI counterparts. Following this pathway, heterostructures based on III–V DMS were found to have higher Curie temperature. In this work, we propose geometrical arrangements that maximize spin separation combining strained and DMS III–V layers.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
68.65.Ac Multilayers
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.Dc Spin polarized transport in semiconductors
72.25.Mk Spin transport through interfaces
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Room temperature ferromagnetism in anatase Ti0.95Cr0.05O2 thin films: Clusters or not?

Nguyen Hoa Hong, Antoine Ruyter, W. Prellier, and Joe Sakai

Appl. Phys. Lett. 85, 6212 (2004); http://dx.doi.org/10.1063/1.1841457 (3 pages) | Cited 14 times

Online Publication Date: 15 December 2004

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Laser ablated Cr-doped TiO2 thin films grown on LaAlO3 substrates are single phased anatase and room temperature ferromagnetic. The magnetic moment of Cr-doped TiO2 films is rather large, and it is consistent with the theoretical predictions. Magnetic force microscopy measurements certainly suggested that the strong ferromagnetism at high temperature in Cr-doped TiO2 films is intrinsic, and it must originate from the diluted magnetic matrix but not from any form of clusters.
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75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.37.Rt Magnetic force microscopy (MFM)

Molecular-beam epitaxy of (Zn,Mn)Se on Si(100)

T. Slobodskyy, C. Rüster, R. Fiederling, D. Keller, C. Gould, W. Ossau, G. Schmidt, and L. W. Molenkamp

Appl. Phys. Lett. 85, 6215 (2004); http://dx.doi.org/10.1063/1.1841456 (3 pages) | Cited 3 times

Online Publication Date: 15 December 2004

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We have investigated the growth by molecular-beam epitaxy of the II–VI diluted magnetic semiconductor (Zn,Mn)Se on As-passivated Si(100) substrates. The growth start has been optimized by using low-temperature epitaxy. Surface properties were assessed by Nomarski and scanning electron microscopy. Optical properties of (Zn,Mn)Se have been studied by photoluminescence and a giant Zeeman splitting of up to 30 meV has been observed. Our observations indicate a high crystalline quality of the epitaxial films.
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81.05.Dz II-VI semiconductors
75.50.Pp Magnetic semiconductors
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
78.20.Ls Magneto-optical effects
75.30.Cr Saturation moments and magnetic susceptibilities
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
75.70.Ak Magnetic properties of monolayers and thin films

Spin injection, diffusion, and detection in lateral spin-valves

Y. Ji, A. Hoffmann, J. S. Jiang, and S. D. Bader

Appl. Phys. Lett. 85, 6218 (2004); http://dx.doi.org/10.1063/1.1841455 (3 pages) | Cited 61 times

Online Publication Date: 15 December 2004

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We demonstrate the injection of spin-polarized electrons into paramagnetic Au nanowires by driving an electric current from a ferromagnetic permalloy (Py) electrode. The nonequilibrium spin accumulation in Au results in a difference between the chemical potentials for spin-up and spin-down electrons that is detected as a field-dependent voltage signal using a second Py electrode. The magnitude of the voltage contrast (>10%) and its coincidence with the magnetic switching of the Py electrodes attest to the spin-sensitive origin of the signals. By increasing the separation of the Py injector and detector, we observe an exponential decay of the spin signals. The measurements yield a spin-diffusion length of 63±15 nm and an injected spin polarization of 3% in Au at 10 K.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.47.Np Metals and alloys
75.50.Bb Fe and its alloys
75.20.En Metals and alloys
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Tt Fine-particle systems; nanocrystalline materials
61.46.-w Structure of nanoscale materials
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